The present invention relates generally to liquid dispensing systems for dispensing liquid material onto substrates and, more particularly, an apparatus and method for use in coating elongated bands of elastic or non-elastic material with an adhesive prior to attachment of the band to a substrate.
In the manufacture of disposable diapers, adult incontinence pads and other hygienic articles, it is often desirable to provide a stretchable portion on the article, such as a waist band or leg, so that a relatively tight fluid seal between the article and the body can be formed. Generally, these stretchable portions are formed by bonding stretched elastic strands or bands directly to the fabric with adhesive so that as the strands or bands contract, the fabric is bunched together to form stretchable regions in the fabric. Alternatively, the stretchable strands or bands are bonded to a web of waistband or leg cuff material which is then bonded to selected areas of the article to form stretchable regions in the fabric.
A typical elastic band includes opposite major surfaces that are generally flat and a pair of opposite sides edges that extend between the pair of flat major surfaces. The band is bonded to the fabric by guiding the band toward a dispensing outlet of a liquid adhesive dispenser that dispenses a continuous bead or filament toward the band. The dispensing outlet is provided on a pattern die of the liquid dispenser and is disposed above and spaced from the elongated band as the band travels in the machine direction (MD). The pattern die is configured with multiple air outlets associated with the dispensing outlet to form air jets or process air that causes the pattern of the dispensed bead to expand in the cross-machine (CD) direction during its flight toward the band.
The liquid dispenser has a guide wheel positioned upstream of the dispensing outlet that guides the band in registry with the dispensing axis of the outlet so that the outlet dispenses the continuous bead of adhesive onto the band. The bead of adhesive may be dispensed in a swirl, cross-stitch or other overlapping or non-overlapping pattern toward the band so that the pattern of the dispensed bead expands in the cross-machine direction during its flight toward the band so that the pattern of the bead extends slightly beyond the side edges of the band. The bead of adhesive contacts and wraps around the band to coat the opposite major surfaces of the band prior to its attachment to the fabric. The bead contacts the band at spaced intervals which are determined by the velocity of the band in the machine direction (MD) and the frequency of the dispensed continuous bead. The spacing of the intervals is decreased with either a decrease in the velocity of the band or an increase in the frequency of the dispensed bead. The bead wraps around the band due to the momentum of the bead as it folds around the side edges of the band.
In the past, the guide wheel has guided the band toward the dispensing outlet so that the band lies in a generally horizontal plane transverse to the dispensing axis of the outlet. The outlet dispenses the continuous bead toward the band so that the bead engages the major surface of the band facing the outlet and then wraps around the band to coat the opposite major surface.
Known guide wheels and methods of coating elongated bands with liquid material suffer from several shortcomings and drawbacks. The horizontal orientation of the band relative to the dispensing outlet requires a broad bead pattern to be dispensed toward the band so that the bead properly wraps around the edges of the band. This broad pattern reduces the frequency at which the bead can be dispensed toward the band which, in turn, reduces the effective coating on the major surfaces of the band. Additionally, the horizontal orientation of the band and the associated broad bead pattern causes the dispensed bead to be susceptible to small changes in the pattern air and the location of the band relative to the dispensing axis of the outlet.
Therefore, there is a need for an improved guide for guiding an elongated band toward a dispensing outlet of a liquid dispenser and method for coating an elongated band with liquid material prior to its attachment to a substrate.
The present invention overcomes the foregoing and other shortcomings and drawbacks of guides and methods heretofore known for use in coating an elongated band with liquid material prior to its attachment to a substrate. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
An elongated band to be coated in accordance with the principles of the present invention includes a pair of opposite major surfaces and a pair of opposite side edges extending between the pair of major surfaces. In accordance with one method of the present invention for coating the elongated band with liquid material dispensed from an outlet of a liquid dispenser, the band is moved in a direction toward the outlet with one of the major surfaces of the band facing the outlet. The band is guided spaced from the outlet with one of the side edges of the band positioned closer to the outlet than the other side edge of the band. Liquid material is dispensed from the outlet as a continuous bead or filament toward the band to coat the major surfaces of the band with the liquid material.
The bead of adhesive may be dispensed in a swirl, cross-stitch or other pattern toward the band so that the pattern of the dispensed bead expands in the cross-machine direction during its flight toward the band so that the pattern of the bead extends slightly beyond the side edges of the band. The pattern of the dispensed bead may be overlapping or non-overlapping upon contact with the band. The bead of adhesive contacts and wraps around the band to coat the opposite major surfaces of the band prior to its attachment to the substrate.
In accordance with another method of the present invention for coating an elongated band with liquid material dispensed from an outlet of a liquid dispenser, the band is moved in a direction toward the outlet with one of the major surfaces of the band facing the outlet. The band is guided spaced from the outlet with a dispensing axis of the outlet intersecting the major surface of the band facing the outlet at an oblique angle. Liquid material is dispensed from the outlet toward the band to coat the major surfaces of the band with the liquid material.
A guide in accordance with the principles of the present invention, such as a rotatable guide wheel in one embodiment, is adapted to be mounted on a shaft for guiding an elongated band toward an outlet of a liquid dispenser capable of dispensing liquid material onto the band. The guide wheel includes a guide wheel body and a tapered surface formed on the guide wheel body that supports the band with one side edge of the band positioned closer to the outlet than the other side edge of the band. A second tapered surface is formed on the guide wheel that engages one of the side edges of the band.
Tilting of the band to position one side edge of the band closer to the outlet than the other side edge reduces the required pattern width of the bead in the cross-machine (CD) direction to coat the band. The smaller pattern width enables a higher frequency dispensing pattern to be used which improves coating of the band since the bead contacts the band at relatively small intervals. In addition, the tilted orientation of the band improves wrapping of the bead around the band to coat the opposite major surfaces of the band.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.